HG-AFS Determination of Lead and Mercury in Soil and Biological Samples with Microwave Assisted Sample Digestion

HG-AFS was applied to the determination of lead and mercury in soil and biological samples. The sample was digested with 4 mL of HNO3 and 1 mL of H2O2 in a microwave digestor under the prescribed conditions. The sample solution after digestion was diluted to 25 mL and used for HG-AFS analysis. Mixture of 30 g·L-1 citric acid solution and HNO3 (1+99) solution was used carrier. Considering chemical reactivity of Pb(Ⅱ)-ion and acidity required by the sample solution, a mixed solution containing 15 g·L-1 of KBH4, 10 g·L-1 of K3Fe(CN)6 and 20 g·L-1 of KOH was used as the reductant. Detection limits (3s/k) found were 0.512 μg·L-1 for Pb(Ⅱ) and 0.067 μg·L-1 for Hg(Ⅱ). Three substantial samples were analyzed by this method, an using these samples as matrixes, test for recovery was made by standard addition method, values of recovery found were in the ranges of 91.0%-97.0% for Pb(Ⅱ) and 88.0%-95.5% for Hg(Ⅱ).